An incubation period is relatively constant for a particular infectious agent. Does that apply to a latent period also?
If you are speaking about a singular, particular infectious agent, yes the latent period, which is the amount of time between being infected and showing signs or symptoms of the illness, is fairly consistent. Depending on the body chemistry of the individual infected, there are reasonable parameters of time that could be presented with reasonable accuracy in predicting the latent period of the infectious agent.
If you are speaking about all infectious agents, the answer is no, because one of the things that identify the infectious nature of the infectious agents is the length of time it takes (latent period) before symptoms of their illnesses present themselves. There are agents that take mere minutes to start manifesting themselves within a host organism. There are also agents that take years before they present the symptoms of illness. So it depends on which agent you are talking about. A cold virus will make you sick in a day or less, while the AIDS virus may take years to break down the human immune system and cause symptoms to start appearing.